Any deviation from specified temperature requirements during storage or transport, documented through continuous monitoring as evidence of cold chain failure. For frozen products, excursions above -12°C compromise safety margins; excursions above -5°C trigger accelerated quality degradation through recrystallization; excursions above 0°C constitute complete cold chain failure requiring product evaluation or rejection.
Excursion Severity Classification
| Temperature Range | Duration | Classification | Action Required |
|---|---|---|---|
| -15°C to -12°C | < 30 min | Minor deviation | Document, continue |
| -15°C to -12°C | > 30 min | Moderate excursion | Evaluate product |
| -12°C to -5°C | Any | Significant excursion | Quality assessment required |
| -5°C to 0°C | Any | Severe excursion | Food safety evaluation |
| Above 0°C | Any | Critical failure | Product rejection likely |
Cumulative vs Single Event Damage
Temperature excursions cause damage through two mechanisms:
Single Event Damage
- Sudden warming triggers rapid recrystallization
- Partial thawing releases drip loss
- Microbial growth initiates above -5°C
- Surface deterioration from moisture migration
Cumulative Damage
- Multiple minor excursions compound over product life
- Each excursion advances recrystallization progression
- Temperature cycling more damaging than stable warmer storage
- Quality degradation invisible until thawing reveals damage
South African Excursion Sources
Common excursion causes in South African operations:
Equipment Failures
- Undersized refrigeration for altitude conditions
- Defrost cycle problems allowing temperature drift
- Compressor failure from overwork
- Thermostat malfunction or calibration errors
Operational Failures
- Excessive door opening frequency without recovery time
- Inadequate pre-cooling before route start
- Loading warm product from inadequate cold storage
- Extended stationary periods in direct sunlight
Environmental Factors
- Summer temperatures exceeding design temperature assumptions
- Urban heat island effects beyond specifications
- Load shedding interrupting cold storage
- Traffic delays with vehicle stationary in heat
Documentation Requirements
R638 compliance and food safety best practices require:
- Continuous temperature logging throughout transport
- Excursion alerts with timestamp and duration
- Documented response actions taken
- Temperature records retained for traceability
- Clear handoff documentation at transfer points
Without documentation, excursions remain undetected. Products may arrive frozen but already damaged—with no evidence explaining subsequent quality complaints.
The Hidden Excursion Problem
Products can experience significant temperature excursions yet arrive at delivery appearing normal:
- Core temperature remains low while surface warms
- Refreezing after excursion restores apparent frozen state
- Recrystallization damage invisible until thawing
- Customer blames delivery when damage predates pickup
Professional cold chain integrity requires proving what didn’t happen (excursions) through continuous documentation—not just checking arrival temperature.
Related Terms: Cold Chain Failure, Temperature Monitoring System, Recrystallization